public class demo5 {
    //大数加法
    public String solve (String s, String t) {
        StringBuilder ret = new StringBuilder();
        int i = s.length()-1, j = t.length()-1;
        int tmp = 0;
        while(i >= 0 || j >= 0 || tmp >0){
            if (i >= 0) tmp += s.charAt(i--) - '0';
            if (j >= 0) tmp += t.charAt(j--) - '0';
            ret.append((char)(tmp %10 + '0') );
            tmp /= 10;
        }
        return ret.reverse().toString();
    }
}
